A major culprit? Hot roofs baked by the sun. The solution? Cooling down those roofs by using reflective surfaces — and doing so even if those cities are covered in snow for several months of the year.

A new study published by Concordia researchers in Energy and Buildings confirms that, contrary to the belief that cool roofs won’t work in colder climates, they actually provide net energy — and monetary — savings.

“Our research shows that any improvement to a roof that limits the summertime solar heat gain actually results in energy-cost savings for the building owner, as well as a reduction in the building’s overall environmental impact.”

For the study, Akbari and his co-author, Mirata Hosseini, a Concordia PhD candidate, used modelling software to simulate energy consumption for several prototype office and retail buildings in four cold-climate cities in North America: Anchorage, Milwaukee, Montreal and Toronto. They found that cool roofs for the simulated buildings resulted in annual energy expenditure savings in all municipalities.

A cool roof on a new, medium-sized office building would save four dollars per 100 square metres in Montreal, $10 per 100 square metres in Toronto and $14 per 100 square metres in Milwaukee and Anchorage. The research also showed that cool roofs can reduce the peak electric demand of the retail buildings by up to five watts per square metre.

“Our study proves that cool roofs for commercial buildings are a net saver of energy in all climates that use air conditioning during the summer,” says Akbari.

“In cooler climates, installing cool roofs may even prevent buying an air conditioner altogether. Even in non-air-conditioned buildings, cool roofs improve comfort during hot summer days. And in extreme cases, these roofs may even save lives by reducing the risk of heat stroke.”

Many municipalities already prescribe cool roofs in the construction of new buildings and for re-roofing existing buildings. This study proves that those rules should also apply in colder climates. It is Akbari’s hope that cool roofs become the global standard.

“On a large scale, cool roofs can moderate the air temperature surrounding a building, decrease greenhouse gas emissions and mitigate the urban heat island effect,” he says.